No, she doesn't have any siblings.
I don't know from where I know it, but I'm sure she was the only child of her parents.
I think that her mother died while giving her birth.
Then her father died in battlefield.
She became orphan, and that's why Dermail raised her.
Than he died, too, and she was left alone.
But I'm sure that Quatre took good care of her
...
NO Mellie and Angel, don't even try to start that game with killing G-girls and taking their boys!!! (you know too well whatI mean

)